1. Technical Field of the Invention
The present invention relates to a method for taking program data for a non-volatile semiconductor device that conducts a page programming in word line units, such as a NAND type flash memory.
2. Conventional Technology
FIG. 4 shows a circuit diagram of a non-volatile semiconductor integrated circuit in accordance with a conventional example. FIG. 5 shows an output waveform diagram of a counter circuit of the non-volatile semiconductor integrated circuit in accordance with the conventional example. Further, FIG. 6 shows a timing chart for taking program data in the non-volatile semiconductor integrated circuit in accordance with the conventional example. A counter circuit 1 shown in FIG. 4 is formed from flip-flop circuits 2-10. Also, reference numeral 11 denotes a column decoder. The flip-flop circuits 2-10 are connected to an internal power supply VDD and a GND power supply.
Generally, in a NAND type flash memory, a programming operation is conducted for all memory transistors together that are connected to selected word lines. In other words, a page programming is conducted in word line units. At present, the size of a page is usually 512 bytes. Accordingly, the column decoder 11 receives column address signals A0-A8 from the counter circuit 1, and conducts column address selections for 512 addresses. Program data is input and retained in each of the selected column addresses.
An operation of the above is described. As shown in FIG. 6, first, a program mode is set at a rising of a write enable signal XWE to the H level while an address latch enable signal ALE is at the L level. Next, a row address is set (to select a word line) at a rising of the write enable signal XWE to the H level while the ALE signal is at the H level. Next, while the ALE signal is at the L level, program data are successively taken in at each rising of the XWE signal to the H level for one page, in other words, from address 0 to address 511. Then, actual programming operations are executed on the memory transistors. The column address signals A0-A8 are generated by the counter circuit 1 using an input of the XWE signal as shown in FIG. 4, and counted in synchronism with the fallings of the XWE signal. The outputs of the counter circuit 1 in FIG. 4 are calculated such that, as shown in FIG. 5, at the first rising of the XWE signal to the H level, all of the signals A0-A8 are at the L level to select column address 0; at the second rising, only the signal A0 is at the H level to select column address 1; and at the 511th rising, all of the signals A0-A8 are at the H level to select column address 511
The conventional technology described above has a problem in that taking program data for one page takes a long time because one data is taken in at each one cycle of the XWE signal. For example, when one cycle is 50 ns, it takes as long as 25.6 xcexcs, which amounts to a substantial proportion against the overall programming time including the actual programming operation time, and therefore is problematical because this makes it difficult to achieve a shorter overall programming time. Also, since outputs of the counter circuit are provided by flip-flop circuits that are connected in multiple stages, there are substantial delays in the outputs, which present a major obstacle to increasing the frequency of the XWE signal in an effort to shorten the time for taking program data.
The present invention is provided to solve such problems, and one object is to shorten the time for taking program data, and shorten the overall programming time.
A non-volatile semiconductor integrated circuit in accordance with the present invention comprises a counter circuit that generates column addresses in synchronism with an external clock, and conducting a page programming sequence in word line units, wherein, when inputting program data, the program data is taken in synchronism with the fallings and risings of the external clock.
Also, a second non-volatile semiconductor integrated circuit in accordance with the present invention is characterized in that, in the first non-volatile semiconductor integrated circuit, the counter circuit that generates column addresses in synchronism with an external clock is driven based on a power supply voltage that is higher than an internal power supply voltage.
Also, a third non-volatile semiconductor integrated circuit in accordance with the present invention is characterized in that, in the second non-volatile semiconductor integrated circuit, the power supply voltage that is higher than the internal power supply voltage is provided by a step-up power supply that is formed based on the internal power supply voltage or an external power supply voltage.
Also, the third non-volatile semiconductor integrated circuit in accordance with the present invention is characterized in that, in the second non-volatile semiconductor integrated circuit, the power supply voltage that is higher than the internal power supply voltage is supplied by an external power supply voltage.
By the means described above, program data is taken in synchronism with the risings and fallings of an external clock, such that the time for taking program data can be shortened by half.
Also, the counter circuit that counts the external clock is driven by using a power supply voltage that is higher than the internal power supply voltage, such that operation delays in the counter circuit are reduced, the frequency of the external clock can be increased and thus the time for taking program data can be further shortened.